April 18, 2021

3D surface vacuum jig gasket

3 min read
I’ve been designing (playin with cad)…. due to the need to eventually manufacture I’m now...

I’ve been designing (playin with cad)…. due to the need to eventually manufacture I’m now problem solving.

Basicaly I have a cube, with its surfaces altered and I have done 2x test faces, I can achive a fit that allows it to stick together with fluid in aluminium with no polishing, however I would like to make a few full cubes and I have settled on 2 options for machining given I only have 3 axis CNC.

1: Machine 5 faces with a lolly-pop mill, and make sets of pre machined soft jaws to match (or face plates to go on the hard jaws) then invert the cubes and machine final face – seems expensive in my mind, also moving the soft jaws orientation after machining is asking to introduce errors imo.

2: Using round stock machine 3 faces (on the diamond/with Z though furthest corner to other furthest corner) then machine matched vacuum jigs to invert and machine final 3 faces. Due to the need for a seal I had been wondering about PTFE tube, I have found 40od 20id for a reasonable price. Due to the average angle of a face being 54 degrees from horizontal this give quite a significant size of face and I am concerned I will not get a seal. Adding machinable channels for foam seal is where I am stuck, and I have been looking for a waterproof, but removeable spray to aid the vacuum seal, non-setting or appliable to the jig then left to go off. I would like to make some in wood, but when machining metals I work with coolant so I may need different things, but I am hoping I can get the wood to stick, with either a shop vac or the venturi and no additional sealant that may contaminate the surface. Metals are the real issue

I did think about the hair spray type stuff from our 3d printer, but I’d rather not come back after a days surfacing to find my part has welded itself to the jig, its pretty darn strong stuff.

PVA glue would mean running dry and potentially soaking parts to release them.

I seen a heat-activated-putty-glue-stuff-thing on the vacuum table retailers’ site, I’ve never used it does anyone have experience of it? When they demonstrated it holding a coconut, they just used it as a glue, when machining a plate they just placed it round the outside of the part, not in-between surfaces, I think it goes back to solid once set, and joins parts together like a glue or silicone seal. I’m not sure how easy it would be to remove a part and reload they never showed it being removed from the coconut, they did show the coconut being smashed with a hammer though, never moved, good demo :).

a spray grease or PTFE spray may be acceptable on metal, not sure how they handle vacuum’s though.

Image attached of jig, orientated to highlight the surface shape and acute angle, with the beginings of a channel cut into it.

Thanks in advance for any advice.

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